75-03-6

163438-09-3

194726-40-4

Under mechanical stirring, (R)-1-(tert-butoxycarbonyl)piperidine-3-carboxylic acid (1 kg, 4.36 mol) was dissolved in N,N-dimethylacetamide (3 L), followed by addition of potassium carbonate (0.664 kg, 4.80 mol). The resulting suspension was stirred at room temperature for 30 min. Ethyl iodide (0.75 kg, 4.80 mol) was slowly added through the addition funnel and stirring was continued at room temperature for 15 min, followed by warming to 50 °C and stirring for 1 h. The reaction was carried out by thin layer chromatography (TLC). The reaction process was monitored by thin layer chromatography (TLC, unfolding agent ratio ethyl acetate:hexane=1:1). Upon completion of the reaction, the reaction mixture was cooled to room temperature and diluted with ethyl acetate (5 L). Insoluble material was removed by diafiltration and the wet filter cake was washed with ethyl acetate (5L). The filtrates were combined and mixed with 5% w/v sodium thiosulfate solution (15L) with stirring, and the organic phase was separated by layering. The aqueous phase was extracted once more with ethyl acetate (5L). All organic layers were combined, washed with water (5L) and dried with anhydrous sodium sulfate. The organic phase was concentrated under reduced pressure to give a semi-solid product, which solidified on standing to ethyl (R)-1-Boc-piperidine-3-dicarboxylate in a yield of 1.1 kg and 99.5%.